Germanium–Tin Junction Formed Using Phosphorus Ion Implant and 400 Rapid Thermal Anneal

AGe_0.976Sn_0.024 n⁺/p diode was formed using phosphorus ion (P⁺) implant and rapid thermal annealing at 400°C. Activation of P in Ge typically requires high temperatures (e.g., 700°C), and it was found that this is not needed in the presence of a small amount of Sn. A high forward bias current of 320 A/cm² at -1 V is achieved for the Ge_0.976Sn_0.024n⁺/p diode. This is four times higher than that of the Ge n⁺/p control diode, which received the same P⁺ implant but activated at 700°C. The n⁺-GeSn region has a high active dopant concentration of 2.1 × 10¹⁹× cm^-3, much higher than that in the Ge control. The increased active dopant concentration in GeSn reduces the width of the tunneling barrier between the Al contact and the n⁺-GeSn and increases the forward bias diode current. Enhancement of P activation in Ge_0.976Sn_0.024 could possibly be as a result of passivation of vacancies in the Ge lattice due to Sn atoms.